The clinical promise for 3D display of medical images that is indicated by the work of us and others will be brought to fruition by providing a greater degree of interaction; integration with 2D display; and improved object definition methods. Based on our already developed systems for 3D display and interaction, we will develop display approaches in both major areas: reflective and self-luminous; develop methods of immediate user interaction in display and object definition; and develop methods combining both interactive and automatic 3D segmentation. In particular, we will work on varifocal mirror and shaded graphics displays with a beginning development of headmounted displays for medical imaging. These systems will be integrated with 2D displays capable of clearly showing slice grey-scale in a way such that interaction can naturally occur on the integrated 2D/3D system. Clinical problems of brain tumor and intestinal lesion visualization, and radiotherapy treatment planning will guide the research directions and serve to evaluate it.